1. Field of the Invention
The invention relates to a projection type display device which separates a white beam from a light source into beams of three colors, i.e., red, blue and green, modulates each color beam through a light valve such as a liquid crystal panel in accordance with image information, synthesizes the modulated color beams by light synthesizing means, and projects the synthesized beams onto a projection surface through projecting means in an enlarged state. More specifically, the invention relates to a mechanism for mounting a liquid crystal panel to a prism composite constituting a light synthesizing mechanism of a projection type display device.
2. Description of Related Art
In a conventional projection type display device, a liquid crystal panel, serving as a light valve, is mounted to a light incident surface for each light beam of a prism composite. The prism composite is a light synthesizing mechanism. A conventional mechanism for mounting a liquid crystal panel to a prism composite is disclosed in Japanese Unexamined Patent Publication No. 6-118368. In this type of mounting mechanism, the liquid crystal panel, which serves as the light valve, is directly glued and fixed to the light incident surface of the prism composite by an adhesive.
When the light valve is directly glued and fixed to the light incident surface, it is possible to omit the mutual pixel matching mechanism (alignment) of multiple light valves which modulate the light beam separated into red, green and blue colors. It is also possible to omit the focus adjusting mechanism (focus adjustment) so that each image formation plane constituting the subject is positioned within the permissible depth of focus of the projection lens. Thus, it is possible to reduce the size, weight and number of parts of the optical system of the projection device.
However, when the light valve is directly glued and fixed to the light incident surface of the prism composite, several problems may arise. These problems are outlined below.
First, when external light enters the interior of the device, there is a possibility that the external light will enter the light valve. When the light valve receives such light, there is also a possibility of each element of the light valve malfunctioning.
Second, directly touching the light valve while treating the light valve is not desirable since that will lead to problems such as breakage. For example, when the light valve is glued to the prism composite, chucking the light valve directly with a jig may lead to the edge, corner, etc. of the light valve being damaged. Additionally, it is not desirable for the operator to hold the light valve directly by hand and glue it to the prism composite because the light valve, such as a liquid crystal panel, is also vulnerable to static electricity.
Third, the light valve, which is glued to the prism composite, can generate a defect in a part of its pixels as a result of changes with time. When a defect has been generated in the light valve, it is necessary to replace it with a new one. However, since the light valve is glued and fixed to the prism composite, it is difficult to replace only the light valve having the defect. That is, it is not easy to detach the liquid crystal panel glued and fixed to the light incident surface of the prism composite without damaging the light incident surface. For this reason, it is necessary in some cases to also replace the prism composite. The replacement of the prism component, however, is not economical.
It is an object of the invention to provide a projection type display device equipped with a light valve mounting mechanism capable of solving the above-described problems.
To achieve the above object, the invention is a projection type display device which separates a beam from a light source into a plurality of beams of various colors. The projection type display device modulates each color beam through a light valve in accordance with image information, and thereafter synthesizes the modulated color beams by light synthesizing mechanisms. The projection type display then projects the synthesized beam onto a projection surface, through a projecting mechanism, in an enlarged state. At this point, the periphery of the light valve is protected against the intrusion of external light, damage, etc. By utilizing this type of projection display, it is not necessary for the light valve to be directly glued or otherwise fixed to the light synthesizing mechanism.
In accordance with the invention, the projection type display device includes a fixation frame plate fixed to a light incident surface of the light synthesizing mechanism. The projection type display further includes a light valve frame plate for holding the light valve, a fixing mechanism for detachably fixing the light valve frame plate to the fixation frame plate, and a positioning mechanism for positioning the light valve.
Additionally, at least one of the light valve frame plate and the fixation frame plate includes a peripheral wall covering the periphery of the light valve.
The positioning mechanism may include an adjusting member for adjusting the position of the light valve. In this case, it is desirable for the light valve frame plate to be provided with an adjusting guiding mechanism.
In order for the adjusting member to be easily handled with a jig or similar mechanism, it is desirable for the adjusting member to be equipped with at least one engagement section. The engagement section will be utilized when chucking the adjusting member.
Further, it is desirable for the positioning mechanism to be provided in the vicinity of the center of opposite side portions of the light valve frame plate. This configuration avoids stress concentrations due to thermal deformation of the member constituting the object of positioning.
In order for the fixation frame plate and the light valve frame plate to be easily handled with a jig or similar mechanism, it is desirable for the fixation frame plate and the light valve frame plate to be equipped with an engagement section for chucking the plates.
In addition to the fixation frame plate and the light valve frame plate, an intermediate frame plate is disposed between the fixation frame plate and the light valve frame plate. In this case, the intermediate frame plate is fixed to the fixation frame plate by the fixing mechanism.
In this case, a temporal fixing mechanism is provided for temporarily fixing the intermediate frame plate and the light valve frame plate. It is desirable that the intermediate plate, temporarily fixed by the temporal fixing mechanism and the light valve frame plate, be positioned by the positioning mechanism. This makes it possible to perform the temporal fixing operation in the temporarily fixed state, thereby allowing the positioning operation to be easily performed.
The temporal fixing mechanism may include an engagement protrusion formed on either the intermediate frame plate or the light valve frame plate. An engagement hole will be formed in the plate that does not include the engagement protrusion. In this case, the plates can be temporarily fixed by an adhesive.
Even in the case in which an intermediate plate is provided, the positioning mechanism may include adjusting parts for adjusting the position of the light valve. Further, the light valve frame plate may be provided with an adjusting member guiding mechanism. The adjusting parts may be equipped with at least one engagement section used when chucking the adjusting member. The positioning mechanism may be provided in the vicinity of the center of opposite side portions of the light valve frame plate.
In accordance with the invention, the light valve may be placed between the light valve frame plate and the fixation frame plate.
In accordance with the above-described projection type display device, the light valve is held by the light valve frame plate. Further, the fixation frame plate is fixed to the light incident surface of the light synthesizing mechanism, and the light valve frame plate, holding the light valve, is detachably fixed to the fixation frame plate. This can be accomplished directly or through the use of the intermediate frame plate.
Thus, when a defect is generated in the light valve as a result of change with time, the light valve frame plate holding the light valve is detached from the fixation frame plate which is fixed to the light synthesizing mechanism. At this time, a light valve frame plate which holds a new light valve is mounted to the fixation frame plate. In this way, the light valve is not directly fixed to the light synthesizing mechanism, so that the light valve can be replaced easily. Further, when performing the replacing operation, the surface of the light synthesizing means is not damaged.
In accordance with the projection type display device, the periphery of the light valve is protected by the light valve frame plate. This permits the light value to be mounted to the light synthesizing mechanism without directly touching the light valve. Thus, it is possible to prevent the light valve from being damaged. Further, by using the above configuration, no external light enters the invention which would cause a malfunction, because its periphery is covered with the light valve frame plate.
A liquid crystal device may be used as the above-mentioned light valve. Further, the invention is particularly effective in the case of a liquid crystal device which is vulnerable to static electricity and which may cause a malfunction when external light strikes the liquid crystal device.
Further, the light valve can be classified into a light transmission type and a light reflection type. When a light reflection type light valve is used, the light synthesizing mechanisms may also serve as a light separation mechanism for separating a beam from the light source into a plurality of beams of various colors.
Two types of projection type display devices are also contemplated. These projections type display devices include a front surface projection type display device and a back surface projection type display device. The projection of the front surface projection type display device is effected from the side on which the projection surface is observed, and the projection of the back surface projection type display device is effected from the side opposite to the side on which the projection surface is observed. The invention is applicable to both types.
When a dichroic prism is used as the light synthesizing mechanism, the light valve is positioned and fixed to the surface of the dichroic prism by using a fixation frame plate, a light valve frame plate, a fixing mechanism and a positioning mechanism. The fixing structure may be applied to a structure such as a camera in which a solid-state image sensing device such as CCD is positioned and fixed to a color separation prism.
Further objects, details and advantages of the invention will be apparent from the following detailed description, when read in conjunction with the drawings.